Japanese patent laid-open No. Hei. 8-175473 discloses a hybrid vehicle that can switch between travel using an electric motor only and travel using an internal combustion engine only depending on travel conditions of the vehicle for the purpose of achieving lowered fuel consumption and lowered exhaust gas pollution. The hybrid vehicle has power from an internal combustion engine transmitted to a drive wheel by means of a V-belt type power transmission unit and a centrifugal clutch, and an electric motor is also connected to this drive shaft via a switching mechanism for carrying out switching of power of the V-belt transmission unit.
With the structure described above, since the centrifugal clutch is arranged between the drive shaft and the V-belt transmission unit, in the cases such as where a person is walking along pushing the vehicle, so called push walking, the V-belt transmission unit normally does not rotate. However, when switching the power source from the engine to the motor, a switching operation is necessary. Also, if regenerative braking is performed using the motor, since there is first the need to perform the switching operation and the centrifugal clutch is kept connected until the rotational speed of the engine falls below a specified value, power from the drive shaft is partially consumed by rotation of the V-belt power transmission unit, and charging efficiency at the time of regeneration is lowered.
Also, in this structure, if a motor for travel (motion) projects from the transmission case housing the V-belt transmission unit in the widthwise direction of the vehicle, there is a possibility of the area around the drive shaft becoming large and there is a desire to reduce the size by arranging the motor inside the transmission case. If the motor and the centrifugal clutch are both large, it is difficult to achieve reduction in size even if they are housed in the transmission case.
The present invention has been conceived in view of the above described situation, and an object of the invention is to do away with the need for a power source switching operation, improved motor regeneration charge efficiency, and improve layout efficiency inside a transmission case.